High power tube



July 21, 1936. L. A. GEBHARD I HIGH POWER TUBE Filed March 22, 1933 2 Sheets-Sheet 1 INVENToR. 61. Q5 Q01/a5 a TTORNEY July21, 1936. L 'AGEBHARD 2,047,959

HIGH POWER TUBE' Filed March 22, 1933 2 Sheets-Sheet 2 r @HNI 5 /f I m 4g/f6 l5 45 /g INVENTOR. 5 Cog/w ci, Qow,

lgnmmi ma AW? rip Patented `luly 2l, 1936 UNITED STATES PATENT OFFECE Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) My invention relates broadly to high power electron tube systems and more particularly to a* construction of double demountable electron tube of the four element type.

.One of the objects of my invention is to provide a high power double electron tube which includes a renewable cathode, control grid, screen grid'and anode asembled in a demountable relation.

vAnotherv object of my invention is to provide a construction of double demountable four element electron tube in which the control grids in? the double tube are telescopically engaged in a position intermediate the length of the tube by .an insulation member mounted within the vessel which encloses the tube electrodes and concentrically of a renewable screen grid electrode..

Still another object of my invention is to pro- Vide aA construction of demountable electron tube arranged for connection in a symmetrical amplication circuit in which a single screen grid is employed for electrostatically shielding a double group of tube electrodes.

-A further object of my invention is to provide a construction of double demountable electron tube wherein a pair of control grids are insulatingly supported from opposite end plates and'adapted to be axially aligned and insulatingly interconnected by a telescopic movement in a position concentrically related to a removable screen grid disposed concentrically with respect tothe anodes of the double demountable tube.

A still further object of my invention is to provide a construction of four element demountable tube in which separable electrostatic shields are connectible with opposite ends of one of the elements in the double electron tube structure.

Still another object of my invention is to provide a construction of screen grid demountable electron tube in which Va single screen grid is mounted inconcentric relation to separate sets of Ycontrol grid and anode electrodes with respect to which a renewable cathode element is axially related.

Other and further objects of my invention re,- side in the construction of a double demountable screen grid tube as set forth more fully in thelspecication hereinafter following by reference to the accompanying drawings, wherein:

Figure 1 is a side'elevation of the double demountablescreen grid tube of my invention with the securing means broken away and with the central portion of the tube broken away and illustrated in section for indicating the adjacent ends of the two anodes and the screen grid therein; Fig. 2 is a vertical cross-sectional view taken )through the double demountable screen grid tube of my invention, portions of the screen appearing in the rear being omitted in this and 5 other iigures to avoid confusion; Fig. 3 is a transverse cross-sectional view taken through the electron tube of my invention on line 3-3 of Fig. 2; Fig. 4 is a fragmentary cross-sectional View in enlarged form showing the upper end of the demountable tube elements of my invention and illustrating the manner of establishing electrical connection to the upper control grid; Fig. 5 is a vertical sectional View of the lower portion of the double demountable screen grid tube of my invention and illustrating the manner of establishing electrical connection to the lower control grid in the tube; Fig. 6 is a cross-sectional View of the upper portion of the double demountable electron tube taken at ninety degrees with respect to the view of Fig. 4 and illustrating the connection for the screen grid electrode; Fig. '7

is a fragmentary cross-sectional view of the lower portion of the tube taken at ninety degrees with respect to the view of Fig. 5 and showing 25 the connection to the screen grid for the lower set of tube electrodes; Fig. 8 is a perspective view of the removable mounting means for the screen grid electrode in the demountable tube; Figs. 9, 10 and ll illustrate modified forms of airtight 30 joints which may be used in the contruction of my invention for insuring an airtight closure within the tube of my invention; and Fig. l2 illustrates a modified form of insulated securing means which may be employed for compressing the end plates upon the ends of the insulated sleeves which are secured over the tubular anode structures in the double demountable tube of my invention.

My invention provides a construction of double demountable electron tube of the screen grid type wherein the parts may be readily disassembled for renewal of deteriorated elements and the replaceable elements restored to position and the tube re-pumped to provide that degree of vacuum re- 4- quired for electronic operation. The electrodes of the tube are compactly assembled, and yet, insulatingly spaced and supported in such relation that breakdown is avoided. The tube comprises end plate members which insulatingly support control grid electrodes of cylindrical structure. The control grid electrodes are telescopically engaged at their adjoining ends over an insulated sleeve element which maintains the control grids in axial alignment. Terminals for each of the control grids are supportedV in insulating relation on each of the end plates. The same screen grid is employed for both sets of electrodes in the tube. The structure of the screen grid is such that the cylindrical ends thereof may be interengaged on sleeve members insulatingly supported from the These sleeve members eachinclude Y end plates. laterally extending electrostatic shields. Y' The cylindrical ends of the screen grid slidably Vfit over the sleeves insulatingly mounted on the end plates and enable the screen .grid to be concentrically disposed within the tube. The anodesfor rthe double tube are each uid cooled. Sleeve members and gaskets of insulation material are employed for spacially mounting the sets o f tube electrodes. Various means are provided for securing the double set of electrodes in assembled relation for permitting a vacuum to be maintained in the closed vessel formed by the electrodes,

The double demountable screen grid'tube o my invention has many economiesover electronV tubes heretofore known in the art Aand is not subject4 to the economic waste encountered in tubes heretofore known. v l

Referringto the drawings in detail, the :filament l of the tube extends Vlongitudinally throughthe center ofthe tube.V T wo control grids `2 and 2 surround thefilament. A single screen grid 3 surrounds the control gridsand extends to the bothends of the tube. Two anodes ande are symmetrically disposed with respect to the other elements and surround the screen grid 3. n

The lament l is secured at its ends by mountings 5 and 5. The construction ofv and method of fluid cooling these mountings andthe manner in which expansion of the iilament is compen satedA isset forth more fully in finy Patent 1,993,724, granted March- 5, 1935. The mounting's are supported from end plates 6 and 6. The filament terminals arefshown at 'Ewand Ea.

'I'he control grids 2 andv2' Yare, supported 'respectively lfrom end plates 6 and 6 in a demcuntable assembly. The 'grids are supported and aligned 'at YVthe center by means of insulating i member 1i. This insulator is'made of magnesium silicate 'or fa' combination of magnesium and aluminum silicate `havinglow radiov frequency loss and good lheat resisting qualities. All other in sulating parts of the tube are Ypreferably made of this material. Insulator l also tends'to shield the electron emission from that portion Yof the filament adjacent to it, thus preventing a flow rof electrons which would otherwise be used in carrying an uncontrolled current tothe anode. The

Y efficiency of the tube from this standpoint is thus improvedl due to the location 'of insulator l. The rings 8 and 8 slip over lshoulders `on insulator l', thus making assembly rof the tube veryveasy'.Y The control grid terminals are shown at Za'and 2a' insulatingly'mounted on end plates E Yand 'Y The screen grid 3 shields the control grids Z and 2 from the anodes. By making the screen grid continuous from one end of the tube to the other, very efficient shielding is obtained. The factthat'the end plates 6 and 6 are of metal also serves to shield the control grids as does the l extension of the screen grid atv its ends, as shown at!!V and 9'.' The mounting of the ends of the' screen grid 3, with respect to the-end plates 5 and "6 respectively, is accomplishedby members disposed in ninety degree spaced relation with rre spectrv to thememb'ers which support the control grids, as illustrated vmore particularly .in Fi'gse and 6.*'In order to permit ready 'assemblyjthe ends of thescreeng'rid gare constructed as's'hown gage the ange 9.

to terminals Zdand'Za.

4in Fig-'7. The screen grid extension'or flange S n Y' Which serves also as a means of support, is tted onto ring lll with a push-iit so that it will make good electrical and mechanical contact.. The end of ring l0 or the shoulder on the extension 9V may be split as shown at ita so as to providerngers having a 'certain amount of spring, thus further insuring goodcontact. The oppositeend of the screen gridis provided with ring lf asshovvn in Fig. 8 having split portions lila Ato resiliently encare must beV taken to provide good Aelectrical and mechanical 'contact without impairing the shield-Y ing function. Screen grid'terminals are shown at H and I l spaced ninety degrees with respect If desired, the center of the ,Y screen may be split to make assembly easy butV The anodes VlV and 4' are cooled by the circulation of a cooling uid through chambers `|72 Yand l2' vformed about the anodes byV cylindrical mem-'1r bers i3 and .|31 The cooling fluid passesintop inlets lll and I4 adjacent tothe joints between the anodes' and their insulating support members, Y

thus insuring the air-tightness ofthe Y,joints by g YAfter Apassing around the 25 Y Y keeping them cool. Y ancdes, the cooling liquid isdischarged at the outletsl5 and l5. The' anodes are supported by insulating lcylindrical membersY l5, Ii'iand I1. Airtight joints are insured 'bythe use of gaskets I8 and |8772 I haveillustratedin Figs. 9, 10 andll 3e various forms of airtightjoints which may l.be employed@ Y c' j y 1 Throughout theV several assembly views of theY tube ofmy invention, I have conventionally .illustratedgaskets at each of the joints which are 35i;VY Y .Y

placed under compressionY :for preventing'fthe leakage oi gas. To simplify the illustrationfofthe invention, these gaskets have been illustrated schematically fin the 'assembly views. However, IA desire thatv it be understood .that in practice, the joints-are Vformed with coasting facesV establishing aiserpentine course through thev ljoint: which substantially prevents*undesirable leakaV Vage and providesa gas tight seal. Fig. 9 shows end plate 6 provided with an annular projection in theV insulator i6. The gasket I8 which is vdis posed Vtherebetween provides a substantial sealV against the leakageof gas. Figfl shows a" 50,' provided with a pair of concentric ribsdepend r Y modified construction in which end plate '-6 ist Csi. Y

lon'faces'd Vand lBd, serves to preventseepageVY Y ofV gas between the joints.. As I Yhave pointed Y out, any `'one of the types-of Vjoint illustrated, for any other form of joint may 5be usedfor insur ing Yagas -tight closure within the anode struc# ture. The tube-is vheldltogethervby longitudinal' support members I9 extending between the end 'mi plates 6 and vliiand fastened'by'screws ZIJ'an'dZU.

ItA will Yalso te understood. that the tensioni members i9- have been :illustrated schematically for the purpose :of 'simplifying Vthe illustration andVv that in`1practice, ,Il g'employ :any suitable iar- 6a 'whichnts' into a coacting annular recess Ila Y rangement of tension adjusting,meansl for compressing the-end platesLS and v against the gaskets i8, insulators I6, :gaskets |-8,vinsulator I1 and V`insulator I6', and against .the anodes 4 and ll.l vOne form 4of tension adjusting means has been illustrated in Fig. 12. In this arrangement, the rod `I9 of insulation material has aV sleeve |9a riveted'. thereto." to provide an Vabutment against end plate 6'. 'Ihe` upper extremity of rod I9 has a sleeve I 9b riveted thereto, which sleeve is externally screw threaded to receive the engaging nut 25 bywhich end plate 6 andthe associated insulators and anodes are maintained in airtightengagement. l/arious forms of turnbuckles may be employed, carebeing exercised to employ insulation means for reducing the distributedV capacity eifects. Anode terminals are provided at 2l and 2|. vacuum pumpis shown at 22.

Suitable means are provided for governing the automatic operationof the vacuum pump for drawing that vacuum in the closed vessel of the tube for maintaining that degree of vacuum required for operation of the electron discharge device.

By reason of the compactness of the construction Vused in this tube and the shortness of its electrical circuits, it can 'be used at much higher frequencies than can an ordinary tube or two ordinary tubes :ini apush-pull circuit. The ei'l'iciency of the tube is greater than ordinary tubes at the limiting frequency of the latter. The arrangement of the screen grid provides excellent shielding and eliminates the use of balance circuits. Ihe arrangement of terminals permits nearly ideal circuit design with respect to symmetry.

Figure 8 shows more clearly the arrangement of the ring member 9 which is secured to the end plate 6 of the demountable electron tube. The ring member 9 is insulatingly mounted with respect to the end plate 6 by means of spaced metallic supports represented at 9a and 9b. The metallic support 9a is insulatingly mounted on pedestal insulator 26 supported on end plate 6. 'I'he metallic support 9b is insulatingly mounted on insulated terminal Il and electrically connected with the connector which extends therethrough. The position of the pedestal insulator 26 and the screen grid terminal Il', in diametrically opposite relation, insures the rigid mounting of the screen grid within the demountable tube in concentric spaced relation to the other electrodes in the tube. The pedestal insulator 26 and insulated grid terminal Il' for the screen grid are oiset ninety degrees with respect to the pedestal insulator 2l' and the insulated control grid terminal 2a on the end plate 6. 'I'his arrangement insures complete insulation and rigid mechanical mounting of the several electrodes. The upper end structure of the tube is similarly arranged, that is, control grid 2 is supported by metallic strip members secured to pedestal insulator 21 and insulated terminal 2a, as represented in Fig. 4, while the screen grid is supported by strip members 9a connected to pedestal insulator 26 and strip member 9b connected to insulated terminal Il. The same diametrical spaced relation is maintained between the supports for the control grid and the supports for the screen grid, as heretofore explained with respect to the lower end of the tube.

The insulation material employed in the electron tube of my invention is formed of magnesium silicate or a combination of magnesium and A connection for theY aluminum silicate which is compacted under high pressure and has such negligible porosity that there is no appreciable seepage of air through the insulation material. The insulation material may be machined to provide abutting joints of such character that leakage of air through the joint, particularly when a lead gasket is employed, is practically impossible. Furthermore, automatic control of the vacuum pump enables this Ypump to be operated at successive times for 10 maintaining the required vacuum in the tube.

rThe .screen grid 3 is common to both sets -of electrodes of the electron tube. As will be observed, the same cathode is employed for both sets of electrodes. There are pairs of control grids l5 and anodes associated with the cathode and the common screen grid is disposed intermediate the control grids and the anodes. This arrangement insures a highly compact construction for the electron tube at the same time that the control grids of each of the electron tubes are effectively shielded. In the assembly process, control grids are insulatingly supported on the opposite end plates. These control grids are telescopically engaged by the intermediate insulator l during the assembly of the tube. The screen grid is secured at its lower rend by telescopic engagement between flange 9' and ring ID. At the upper end, the ring lll, carried by the upper end plate 6, provides telescopic engagement with ange 9 30 carried by the screen grid, thereby centering the screen grid rigidly within the electron tube concentric with respect to the cathode, control grids and anodes. Sufficient space is provided by the aperture in the upper end plate 6 to insure the 35 manual alignment of the screen grid with respect to the control grids during the assembly process. 'I'he insulated pedestals which are provided between the end plates and the anges 9 and 9 for insuring the firm mounting of the ilanges 9 and 9 with respect to the end plates 6 and 6 for correspondingly facilitating the concentric engagement of the opposite ends of the screen grid with respect to the anges 9 and 9 are so spaced as not to interfere with the manual adjustment necessary for mounting a new lament in position. In all instances, the insulated pedestals which provide supports for the ends of the screen grid are oifset from and maintained out of the path of the insulated pedestals which provide supports for the control grids with respect to the end plates.

The assembly of the parts of the double tube of my invention is very practical in the form illustrated, but I fully appreciate that various modiii- 5 cations may be made by those skilled in the art and I intend no limitations upon my invention other than are imposed by the scope of the appended claims.

The invention herein described may be manufactured and used by or for the Government of the United States of America for Governmental purposes without the payment of any royalty thereon or therefor.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

l. A high power electron tube comprising a pair of end plates, alternately disposed insulating members and anodes stacked between said end plates, a replaceable cathode supported between said end plates axially of said anodes, a plurality of control grids, one of said control grids insulatingly mounted on each of said end plates, insulation means interconnecting the intermediate ends of said control grids, a plurality of anged ring-members;- one.- ,orsaid 'ring members insulate ingly mounted witnlrespect, to leach ofl said endl plates-,Y and. a sereen'grid'detaehably engageable with said ring members. and disposed in eoneenfm anodes. Y Y.

21. A high power electron tube comprising a trie Vrelation between lsaid control' grids and pair of end plates,4 alternatelyydisposed insulat-` ing members and anodes Vstacked between .said end plates,y a, replaceable, cathode supported be-A tween saidr end plates aX-ially'of saidv anodes, a

plurality of control' grids,` one of said control grids lnsulatingly mounted on each ofy said end plates; insulationV means interconnecting the intermediate ends of' said control grids, a plurality of .annular-supports, one of said kannular supl-v portsrinsulatinglyfmounted adjacent the inside face. of Veach of said end plates, and a cylindrical i 'screen grid havingfitsfopposite ends detaehablyf engaged with said annular supports whereby said screen grid' is concentricallydisposed- WithV re'` 'speet togsaid eontrol gridssand anodes.`

3; A high power eleetronltube comprising a;

pair ofr end plates, alternately disposedl insulat-V ing members vand anodes stacked betweenV said end plates, a replaceable cathode supported loetweensaid end; plates axially or"V said anodes; a pluralityfof control grids, one of said grids ins sulaqingly mounted ongeach ofsaid end plates, in-

' sulation.l means intereonneetingA the intermediate afnews ends of said control grids, a. plurality of. flanged ring: members, one of said anged ring .members insulatngly supported from the. inside face of each of said end plates and disposed coneentricale lyf about, the or said control. grids, and a.V v5 Y Y Cylindrical cagev-likeyscreeri'grid nayi-ng'its opv posits ends telescopieally engaged over said ring members for removably Yrnoun'rifne said' screen grid `sonesentri@ relffit;v n to saidcontrol gridsirand annees.; j t Y j ,1 L 4s., Asereenf grid electrode, meanstordemevnle'4 ably supporting the screen grid. electrode,y eem.-A

nrisngfa pair Qi. perimetral Supports; to loe-morph Y ed adjae the inneriacesgoftheend portions Y end but. insulated from'. each ober and. @oneens trieallr surrounding .saidieathode,; an anode. elec-f trode individual tofeach of said control Vgrick eleef1 Y tredes, and a screen gfridreleetrode dispersed be- I tween said pair of evontrolgrid:` electrodes and saisirA Y anode electrodes and; commonV to, the'tworsets;

off control gridA andA anode electrodes. i f

1707vv Y,

thsereen rid having its i5' 

